1. Field of the Invention
This invention relates to an air filter for an automotive vehicle fuel vapor recovery system, which includes structures for gradually separating unwanted particles of dust, moisture, soot, and the like from the vapor recovery system purge air stream.
2. Disclosure Information
Conventional fuel vapor recovery systems used in automotive vehicles typically include a carbon canister used to recover excess fuel vapor generated in the fuel tank. Activated carbon in the carbon canister adsorbs the fuel vapor and temporarily retains the vapor until the canister is purged. During vehicle operation, at times determined by programmed vehicle calibration, the fuel vapor adsorbed by the activated carbon is desorbed by introducing outside air, or purge air, to the canister. The fuel vapor thus desorbed is fed to the engine for utilization in combustion. The present invention ensures that the air used to purge the carbon canister, or purge air, is dry and cleaned of particulate matter. This invention has been approved through theoretical calculations, computer simulations, and laboratory and road testing, and is involved in a current production program.
Filtering of-purge air introduced to a vapor recovery system to purge the carbon canister is not new. For the mentioned purpose, prior art examples teach the use of one or more assemblies comprising either a filter medium, baffle means, or both.
U.S. Pat. No. 5,058,693 to Murdock et al, U.S. Pat. No. 5,024,687 to Waller, and U.S. Pat. No. 5,638,768 to Gimby each disclose a remote fuel vapor recovery system filter assembly comprising the combination of baffle and filter element means. Both '693 and '687 include simple baffle means comprising no more than two independent baffle entities. The present invention discloses a plurality of mating and nonmating planar baffles, the increased complexity of which is matched by increased functional efficiency. Patent '768 provides a self-cleaning air filter comprising a filter element of various embodiments. In each embodiment, this mentioned element, so that it may be cleaned by the invention's filter cleaning member, is apparently a thin, firm, screen-like entity, and the filter includes provisions for function upon "occlusion" of this element. The present invention is comprised of a robust and hearty (thick, wide and tall) filter element and a baffle area, and has been proven to be able to last the average lifetime usage of vehicles (approximately 150,000 miles) without any cleaning.
There are two primary and novel factors contributing to the long-lasting functionality of our invention. The first is found in the design of the baffle section. The plurality of baffles are designed such that the particles, having wide size and inertial distributions, are dislodged from the air stream as it travels from inlet towards the filter section. This occurs due to decreased baffle spacing between baffles and the corresponding increase in mobility demand placed on the air flow. The second primary and novel quality of our invention is found in the implementation of a filter element so that the smallest particles (those that survive the baffle section) are generally lodged in the upper half of the filter element and eventually, due to gravity, vibration, etc., will migrate to the lower portions of the element. This occurrence will ensure the thorough cleaning of the air and the long-lasting function of the air filter assembly.
U.S. Pat. No. 4,693,393 to DeMinco et al and U.S. Pat. No. 5,501,198 to Korama disclose examples of filtering systems integrally combined within a carbon canister by comprising only baffle means and only filter element means, respectively. U.S. Pat. No. 5,149,347 to Turner et al also discloses a separator device comprising only a baffle section, which is remotely connected to the carbon canister. It is apparent that any structure comprising only baffle means or only filter means will not bet-as effective and robust as the present invention comprising both baffle and particulate filter means.
It is a feature of the present invention that both graduated baffle separation means and filter element means are included in a filter assembly. This assures a maximum degree of separation of particles, foreign matter, such as soot and road dust, moisture, and the like from the fresh air therein otherwise present.